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Copper vs Aluminum Wiring: Electrical Conductivity Comparison
Copper vs Aluminum Wiring: Electrical Conductivity Comparison
Copper and aluminum are the two metals used for electrical conductors, and the choice between them is not a matter of preference — it is a trade-off between conductivity, poids, cost and installation. Copper is the traditional choice for its conductivity and reliability. Aluminum is lighter and cheaper, but requires different installation practices. This guide compares the two on conductivity, poids, cost, connection reliability and code requirements.
Conductivité: Copper Wins by 60%
Cuivre (C11000 ETP) has a conductivity of 101% SIGC (International Annealed Copper Standard), ou 59.6 × 10⁶ S/m. Aluminium (1350) has a conductivity of 61% SIGC, ou 37.7 × 10⁶ S/m. To carry the same current, an aluminum conductor must be 1.6× larger in cross-section than copper. UN 10 mm² copper wire carries the same current as a 16 mm² aluminum wire. This is why aluminum wiring is always one size larger than copper for the same application. Voir notre Plaque de cuivre C11000 et 6061-Plaque T6.
| Propriété | Cuivre (C11000) | Aluminium (1350) |
|---|---|---|
| Conductivité | 101% SIGC | 61% SIGC |
| Densité | 8.96 g/cm³ | 2.70 g/cm³ |
| Weight for same current | 1.0 | 0.5 |
| Cost index | 1.0 | 0.4 |
| Connection reliability | Excellent | Requires special lugs |
| Thermal expansion | 17 ppm/°C | 23 ppm/°C |
Poids: Aluminum Is Half the Mass
Aluminum is one-third the density of copper. Even though the aluminum conductor must be 1.6× larger in cross-section to carry the same current, the total weight is still 0.5× that of copper. For overhead power lines, this is decisive — aluminum conductors weigh half as much, which means lighter poles, longer spans and lower installation cost. For building wiring, weight is less critical, but for long-distance transmission, aluminum is the standard. ACSR (Aluminum Conductor Steel Reinforced) is the standard overhead conductor — aluminum strands around a steel core, combining aluminum’s conductivity with steel’s strength.
Coût: Aluminum Is 60% Cheaper
Aluminum costs about 40% of copper per kilogram. Even though the aluminum conductor is larger, the total material cost for a given current is about 50 – 60% of copper. For large-scale power distribution, this is a significant saving. For residential wiring, the cost difference is smaller, and the installation issues (see below) outweigh the material savings.
The Connection Problem: Why Aluminum Needs Special Lugs
Aluminum has two issues that make it tricky to install: oxidation and cold flow. Aluminum oxide forms instantly on exposed surfaces and is an insulator — a loose connection in aluminum wire heats up, the oxide grows, and the connection fails. Copper oxide is conductive, so copper connections are more forgiving. Aluminum also cold-flows under pressure: a tightened aluminum connection loosens over time as the metal slowly deforms. This is why aluminum wiring requires special lugs with antioxidant compound and torque specifications. In the 1960s – 70s, residential aluminum wiring in the US caused fires because standard copper lugs were used — the connections loosened and overheated. Modern aluminum wiring (AA-8000 alloy) with properly rated lugs is safe, but it requires more careful installation.
When to Use Which
Use copper for: residential wiring, branch circuits, mise à la terre, électronique, motor windings, and any connection that must be reliable for 50+ years without maintenance. Use aluminum for: overhead transmission lines, large feeder conductors in commercial buildings, and any application where weight matters. For grounding, always use copper — aluminum grounding rods corrode in soil. For busbars in switchgear, copper is standard because it connects reliably and carries high current. For overhead lines, aluminum is the only practical choice because of weight and cost.
